Production of hard and flexible microcrystalline waxes



United States Patent PRODUCTION OF HARD AND MICROCRYSTALLINE WAXES AlanCollier, Sunbury-on-Thames, England, assignor to I The British PetroleumCompany Limited, London, England, a British joint-stock corporation NoDrawing. Application August 6, 1957 Serial No. 676,506 I Y Claims. 01.208-25) "This invention relates to the production of hard and flexiblewaxes from single-stage solvent-recrystallized wax which has beenprepared from so-called bright stock slack wax by single-stagerecrystallization at a temperature within the range 20-60 F. Brightstock slack wax is obtained from the residues of the vacuum stage of"crude petroleum distillation and is often called crude.

microcrystalline wax since it contains a large proportion ofmicrocrystalline wax having good flexibility and good The separatedadduct is preferably washed with fresh wax solvent at the reactiontemperature before being decomposed. Decomposition of the adduct may beeffected by the addition of boiling water which dissolves the urealeaving the adducted portion of the wax in solution in the occluded washsolvent.

The wax solvent used is preferably methyl-iso-butyl ketone (MiBK). UsingMiBK, the wax/solvent ratio should preferably lie within the range from1:5 to 1:10 gm./ml.

A number of examples of the invention will now be described.

' EXAMPLES Single-stage solvent-recrystallized bright stock slack .waxobtained from a Middle Eastern crude oil was dissolved inwater-saturated MiBK in a 1 gm./l0 ml. wax/solvent ratio. The MiBK wassaturated with water by allowing it to be stored over water. The maximumuptake of water by MiBK at room temperature 20 C.), is about 2% byvolume. Solid urea in the weight ratio of 2 parts of urea to 1 part waxby weight was then added. The mixture was then stirred for 20 minutesusing a'disperator-type stirrer at a temperature of 160- .170 F. whenadduction took place. The mixture was then filtered through a stainlesssteel sinter, the retained adduct being washed with fresh MiBK at thereaction temperature. The decomposition of the adduct was effected bythe addition of boiling Water which dissolved the urea, leaving theadducted portion of the wax in solution in the occluded wash solvent.Recovery of the product waxes from the WaX/ solvent phases was carriedout .by distillation of the solvent from the phases. The experiment wasrepeated using reaction periods of 10 minutes and minutes. Theproperties of the waxes produced by these experiments are given in Table1.

Table 1 Solvent: Methyl iso-butyl ketone Solvent/wax ratio: 10/1;rnlJgm. Urea/wax ratio: 2/1; WtJwt.

Reaction Temperature: 160 F./165 F.

Yields, wt. Melting point, Penetration Flexibility,

percent F. 77 F. cycles 0 0. Reaction time, minutes Adduct Non- AdductNon- Adduct Non- Adduet Nonwax adduct wax adduct wax adduct wax adductwax wax wax wax It will be seen that a reaction period of 20 minutes wasthe most advantageous and for maximum adduction, the period should notbe less than this. For a period less than 20 minutes the degree ofadduction was appreciably reduced, while for a much longer period therewas only a small increase in the percentage of wax adducted.

Further experiments were carried out using diiferent.

urea/wax ratios. The results of these experiments are given in Table 2and it will be seen that it is possible Table 2 Solvent: Methyliso-butyl ketone Solvent/wax ratio: /1; mL/gm. Reaction time: minutesReaction temperature: 160 F./165 F.

from a single-stage solvent-recrystallized bright stock slack waxfeedstock, comprising dissolving the feedstock Yields, per- Meltingpoint, Penetratio Flexibility, Index cent wt. F. 77 F. cycles 0 C.differ- Ureawex entgal r o, o wt./\vt Adduct Non- Adduet Non- AdductNon- Adduct Nonadduct wax adduct wax adduct wax adduct wax adduct waxwax wax wax wax The flexibility test is carried out on a machinedesigned to rupture a wax strip by continuous flexing through a constantangle, the flexibility being given by the number of cycles required torupture the strip.

Index differential is 10,000 times the difference between the refractiveindex of the wax at its setting point and 1.4365.

The index differential gives a measure of how farthe refractive index isabove that of normal paraflin hydro carbons (R.I. 1.4365), and a highvalue therefore denotes a relatively high non-normal paraffin content.

I claim:

1. A process for producing hard and flexible waxes from a single-stagesolvent-recrystallized bright stock slack wax feedstock, comprisingdissolvingthe feedstock in a water-saturated wax solvent, adding solidurea, agitating the mixture at an elevated temperature of-- F. to causethe straight chain hydrocarbons. present in the wax to form an adductwith the urea, separating the adduct by filtration, recovering flexiblewax 40 from the filtrate and decomposing the adduct to recover hard wax.

2. A process for producing hard and flexible waxes in water-saturatedmethyl isobutyl ketone, adding solid urea, agitating the-mixture at anelevated temperature of 160-170 F. to cause the straight chainhydrocarbons present in the wax to form an adduct with the urea,separating the adduct by filtration, recovering flexible wax from thefiltrate and decomposing the adduct to recover hard wax.

3. A process according to claim 2, in which the solid urea is added tothe wax solution in the weight ratio of 0.25-3.0 parts of urea to onepart of wax.

4. A process according to claim 2, in which the wax feedstock isdissolved in the water-saturated methyl isobutyl ketone in a wax/methylisobutyl ketone ratio range from 1:5 to"1:10 gun/ml.

5. A process according to claim 2, in which the agitation is carried outfor a period of not less than 20 minutes.

References Cited in the file of this patent UNITED STATES PATENTS2,546,328 Arabian Mar. 27, 1951 2,663,671 Wiles et a1 Dec. 22, 19532,823,172 Rumberger et a1 Feb. 11, 1958

1. A PROCESS FOR PRODUCING HARD AND FLEXIBLE WAXES FROM A SINGLE-STAGESOLVENT-RECRYSTALLIZED BRIGHT STOCK SLACK WAX FEEDSTOCK, COMPRISINGDISSOLVING THE FEEDSTOCK IN A WATER-SATURATED WAX SOLVENT, ADDING SOLIDUREA, AGITATING THE MIXTURE AT AN ELEVATED TEMPERATURE OF 160*170*F. TOCAUSE THE STRAIGHT CHAIN HYDROCARBONS PRESENT IN THE WAX TO FORM ANADDUCT WITH THE UREA, SEPARATING THE ADDUCT BY FILTRATION, RECOVERINGFLEXIBLE WAX FROM THE FILTRATE AND DECOMPOSING THE ADDUCT TO RECOVERHARD WAX.